Tantalum pentoxide (Ta.sub.2 O.sub.5) is an important basic material for the production of electronic components (dielectrics, piezoelectrics and, optoelectronic components). The purity requirements of tantalum pentoxide are particularly high in this field of use. Degrees of purity of more than 99.9% are an entirely usual order of magnitude.
Tantalum pentoxide qualities with a purity of more than 99.99% Ta.sub.2 O.sub.5 can be obtained on the basis of the known preparation processes, such as described e.g. in EP-A 70 642 or U.S. Pat. No. 44 90 340. Because of their coarse-grained nature, however, powder metallurgy or ceramic processing cannot be ensured without problems. On the other hand, in the finely ground state their flow properties are so deficient that inhomogeneities arise within the components during powder metallurgy processing. When tantalum pentoxide powders are used as a constituent of mixtures of different types of metal oxide in particular, the properties described for the tantalum pentoxide powders belonging to the prior art result in great diasadvantages.
Determination and measurement of flowability of metallic powders can be achieved by the procedure set forth in ISO (International Organization for Standardization) standard no. 4490 published in 1978. The International Organization for Standardization is a worldwide federation of national standards institutes. A draft of ISO standard 4490 was circulated to ISO member bodies in June 1977 and at the time of publication of the standard in 1978, it had been approved by twenty-two member countries, including the United States.
In following ISO 4490, flowability is determined by measurement of the time in seconds required for 50 grams of metallic powder to flow through the orifice of a calibrated funnel (Hall flowmeter) of standardized dimensions.
The object of this invention is thus to provide a tantalum pentoxide powder which does not have the disadvantages described.